If you enter a field of play then you must now have insurance - which will mean refs - photographers, players and possibly ancillary cleaning staff, but you only buy it once.
Cover currently is only for UK Sanctioned events so non uk events no, nspl, nspa, superleague, D7s currently no, campaign cup unknown.
I checked with my household and my DJ insurance companies and neither of them will cover me in any way shape or form whilst playing paintball due to the use of a firearm, even though it is an air weapon.